Enclosures for internal combustion engines, such as those used on earthmoving machines and mobile power stations, are designed to minimize the sound levels outside the engine compartment. Typically this is accomplished by adding sound insulation to the wall of the enclosure. However, the engine enclosure must allow for sufficient inlet and exit airflow capacity is to support combustion and to provide cooling air for the engine. Air inlets are provided in the enclosure walls, thereby significantly increasing the sound levels outside the compartment.
It is known in the art to cover the enclosure air inlets and exits with a louver formed of sound absorptive material, typically in the shape of straight or V-shaped slats. It should be noted that although the term "louver" may refer both to a slatted opening and to the slats the themselves, this description for the sake of clarity defines it to be limited to the first described usage.
A problem with this type of silencer is that a trade-off must be made between the desired noise attenuation and the air pressure drop across the panel. If the slats are placed in close proximity to one another, substantial broad-band noise reduction can be accomplished, but tending to increase the pressure loss across the panel and thereby reduce the combustion or cooling airflow through the engine compartment. An increase in fan speed to compensate for the lost airflow increases the fan noise, even to the point of eliminating any net gain in noise attenuation. The present invention is directed to methods and apparatus for addressing one or more of the problems set forth above.